Due to a rich scattering environment of wireless channels in indoor high data rate wireless systems, decreased cell size and distances between nearby base stations (BSs), different transmitter-receiver pairs may generate strong interferences against each other. The strong interferences may severely limit the performance of the wireless system.
The wireless interference is more difficult to deal with the rich scattering environment such as outdoor-to-indoor or indoor environments. The difficulty is due to scattering and a transmitted signal being reflected in multiple directions, which in turn, may increase the interference and significantly degrade the wireless system performance (e.g., spectrum efficiency, system/user throughputs).
Fractional Frequency Reuse (FFR) and beam switching are two different methods used to suppress wireless interferences. However, for outdoor-to-indoor or indoor-to-indoor transmission, the gain obtained by coordinated beam forming from beam switching can be significantly degraded by the rich scattering nature of the radio channels. FFR has been widely used in macro cellular systems, and it can also be used for indoor deployments. Although FFR mitigates interferences, FFR also results in lower spectrum efficiency due to a small frequency reuse factor.